title: Catalytic efficiency of signal peptidase I of Escherichia coli is comparable to that of members of the serine protease family.
abstract: A method for estimating the activity of bacterial signal peptidase I (SPase I) was used to determine its activation energy (E[act]). Pro-OmpA-nuclease A, a hybrid secretory precursor, was purified to homogeneity under denaturing conditions and used as a substrate. This substrate was used to determine the activity of SPase I at different temperatures. The results show that the conformation of the mature domain of the substrate pro-OmpA-nuclease A has no discernible effect on the activity of SPase I. The activity data at a range of temperatures were then used to determine the activation energy using the Arrhenius equation. We have estimated E(act) to be 10.4 +/- 0.6 kcal/mol. This work indicates that SPase I is as catalytically efficient as the His-Ser-Asp family of proteases.
authors.affiliation: Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA.
authors.forename: D
authors.initials: D
authors.lastname: Suciu
authors.forename: S
authors.initials: S
authors.lastname: Chatterjee
authors.forename: M
authors.initials: M
authors.lastname: Inouye
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism*; D008836:Micrococcal Nuclease / Q000378:metabolism; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism; D021382:Protein Sorting Signals / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D008565:Membrane Proteins; D011498:Protein Precursors; D021382:Protein Sorting Signals; C092767:pro-OmpA nuclease A; D008836:Micrococcal Nuclease; D012697:Serine Endopeptidases; C026515:type I signal peptidase